As wireless communications systems continues to evolve, new wireless communications systems are being developed which must be backward compatible with legacy wireless communications system. The level of backward compatibility depends on the system requirements and can relate to control channels, time domain structure, frequency domain structure, signaling messages, feedback messages, synchronization channels, and the like.
In order to make new wireless communication systems as efficient as possible, it is often desirable to limit the number of features from the legacy system that will be carried forward to the new system. Further, at some point in the future, it may be desirable to discontinue support for the legacy devices, therefore eliminating the backward compatibility requirement.
The time domain structure of a legacy wireless communication system is the most common area where backward compatibility must be maintained. The time domain structure of a wireless communication system is tightly coupled with the delay associated with hybrid automatic repeat request (H-ARQ) transmissions. The delay associated with H-ARQ transmissions for new mobile stations must be less than or equal to the delay associated with H-ARQ transmissions for legacy mobile stations. Thus, there is a need for reducing the delay associated with H-ARQ transmissions for new mobile stations, while maintaining the time domain structure of the legacy system.